Method of manufacturing electric incandescent lamp and mount structure therefor

ABSTRACT

THE MOUNT STRUCTURE FOR AN ELECTRIC INCANDESCENT LAMP IS MADE BY FIRST BENDING A LENGTH OF ALEAD-IN WIRE INTO A HAIRPIN-SHAPED WIRE PREFORM WITH ITS BIGHT END PREFERABLY OF GREATER SPAN THAN THE ADJACENT LEG PORTIONS, FUSIONSEALING A GLASS BEAD AROUND THE ADJACENT LEG PORTIONS OF THE HAIRPIN-SHAPED WIRE PREFORM TO TIE THEM TOGETHER, AND THEN MOUNTING A FILAMENT ON THE BIGHT PORTION OF THE HAIRPIN-SHAPED WIRE PREFORM AND SEVERING THE BIGHT PORTION AT A REGION BETWEEN ITS CONNECTIONS TO THE FILAMENT TO DIVIDE THE HAIRPIN-SHAPED WIRE PREFORM INTO TWO SEPARATE LEAD-IN WIRES WITH THEIR SEVERED ENDS OUT OF CONTACT WITH ONE ANOTHER. THE BIGHT FORMING BENDS IN THE LEAD-IN WIRES OF THE MOUNT HAVING A CLOSE SLIDING FIT WITH THE INNER WALL OF THE TUBULAR LAMP ENVELOPE TO CENTER THE MOUNT THEREIN.

Feb. 23, 19W R. .1. AYRES 3,564,681

METHOD OF MANUFACTURING ELECTRIC INCANDESCENT LAMP AND MOUNT STRUCTURETHEREFOR Original Filed April 12. 1967 lnvervto'v: Reginald. d. Agreesy? f is At t orneg US. Cl. 29-2515 8 Claims ABSTRACT OF THE DISCLOSUREThe mount structure for an electric incandescent lamp is made by firstbending a length of lead-in Wire into a hairpin-shaped wire preform withits bight end preferably of greater span than the adjacent leg portions,fusionsealing a glass head around the adjacent leg portions of thehairpin-shaped wire preform to tie them together, and then mounting afilament on the bight portion of the hairpin-shaped wire preform andsevering the bight portion at a region between its connections to thefilament to divide the hairpin-shaped wire preform into two separatelead-in wires with their severed ends out of contact with one another.The bight forming bends in the lead-in wires of the mount have a closesliding fit with the inner Wall of the tubular lamp envelope to centerthe mount therein.

This application is a division of application Ser. No. 630,400, filedApr. 12, 1967, now Pat. No. 3,475,641, patented Oct. 28, 1969.

BACKGROUND OF THE INVENTION This invention relates, in general, to amethod of making an electric incandescent lamp and a mount structuretherefor, which method is particularly suitable for the manufacture ofincandescent lamps of extremely small size.

Electric incandescent lamps of very small size, employing tubular glassenvelopes as small as 45" outside diameter and below and having a lengthas little as A" or less, are in general use at present for variouspurposes. These minute size lamps are customarily made by sealing aglass-beaded lamp mount into one end of a glass tube and then evacuatingthe glass tube through its open other end which is then sealed off tocomplete the lamp assembly. The lamp mounts are generally formed byfusionsealing the glass head around a pair of straight wire leads torigidly tie them together, and then attaching a filament to the innerends of the two wire leads to form the lamp mount.

Because of the extremely small size of the lamp mounts employed in suchminute size lamps, it has been necessary heretofore to fabricate thelamp mounts by painstaking hand processing methods. This is readilyunderstandable when it is considered that the specifications for some ofthese minute size electric incandescent lamps require, for example, theuse of leading-in wires having a wire diameter as little as .010, and aloop or U-shaped coiled filament of tungsten wire having a Wire diameteras little as .0002 to .0003" and having straight end leg portitonsextending endwise from the legs of the U-shaped coiled filament portionand pressed into the inner ends of the leading-in wires. The preciselocating of the straight end legs of such a fine wire filamentlongitudinally alongside and in contact with the straight inner ends ofthe leading in wires, in position for the pressing-in of the filamentend legs thereinto, is an extremely delicate operation which cannot beconsistently performed, with satisfactory results, by present dayautomatic mount making equip- United States Patent Ofice 3,564,681Patented Feb. 23, 1971 ment. Moreover, lateral bending of the inner leadportions of the leading-in wires above the glass head, in order torender feasible the attachment of the filament to the inner leads by anautomatic mount making machine, is not practical in the case of suchminute size lamp mounts because of the extreme shortness of the innerleads, these inner leads having in some cases a length above the glassbead of as little as .030, which length is only around three to fourtimes the wire diameter of the inner leads. Any attempt to form or bendsuch short inner leads to an appreciable degree would result in shalingand cracking of the glass bead tying the two leading-in Wires together.

SUMMARY OF THE INVENTION It is an object of the invention, therefore, toprovide a novel method of making an electric incandescent lamp mountstructure which enables the fabrication of extremely small size lampmounts automatically and with great uniformity and freedom from rejects.

Another object of the inventiton is to provide a novel method of makingan electric incandescent lamp which will assure the supporting andmaintenance of the mount structure thereof in centered position withinthe lamp envelope at all times during the use of the lamp.

Briefly stated, and in accordance with one aspect of the invention, alamp mount is formed by first bending a length of leading-in wire into ahairpin-shaped wire preform having its legs extending approximatelyparallel to one another and its bight portion preferably widened tout soas to be of appreciably greater span than the adjacent portion of thelegs of the wire preform. A glass bead is then fusion-sealed around thetwo legs of the Wire preform, at a region closely adjacent the bightthereof, ISO as to rigidly tie the two legs together, following whichthe opposite ends of the Wire filament are attached to the bight of thewire preform at spaced points therealong. The bight of the wire preformis then severed to divide the wire preform into two separate leading-inwires with their severed bight ends spaced apart so as to be out ofcontact with one another. The severed ends of the bight portion of thewire preform may be displaced so as to be offset, and thus out ofcontact with one another.

In accordance with a further aspect of the invention, both the glassbead and the filament of the mount have their lateral boundaries lyingwholly within the lateral boundaries of the opposite ends of the bightportion of the wire preformed defined by the bends therein, and the spanof the bight portion is such that the opposite ends thereof defined bythe bends in the wire preform have a close sliding fit within thetubular glass envelope of the lamp across the diameter thereof so as tolocate and hold the lamp mount in laterally centered position Within theenvelope.

Further objects and advantages of the invention will appear from thefollowing description of a species thereof and from the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIGS. 1 to 4 are views illustrating the successive steps involved infabricating a lamp mount according to the method comprising theinvention;

FIG. 5 is a top plan view of the lamp mount formed by the methodillustrated in FIGS. 1 to 4;

FIG. 6 is a top plan view of a modified form of lamp mount made by aslightly modified fabricating procedure according to the invention;

FIGS. 7 to 11 illustrate the successive steps involved in sealing themount comprising the invention into a lamp envelope and hermeticallysealing the lamp envelope to form a completed lamp assembly embodyingthe invention; and

FIG. 12 is an elevation of a completed lamp according to the inventionhaving a base mounted thereon.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, infabricating a lamp mount according to the invention, a length ofleading-in wire such as that commonly employed in the lamp art forsealing into glass and known as Dumet wire, is first bent into ahairpin-shaped wire preform 1 having its leg portions 2 extendingsubstantially parallel to one another and its bight portion 3 preferablyof appreciably greater span than that of the adjacent portions of thelegs 2 of the wire preform. For this purpose, the two legs 2 of the wirepreform 1 may be flared out near the bight end 3 thereof, as shown at 4in FIG. 1. A glass bead 5 is then fusionsealed around the two legs 2 ofthe wire preform 1, at a region closely adjacent the bight end 3thereof, so as to embed the legs 2 and rigidly tie them together. Theglass bead 5 may be conveniently formed by slipping a small glass ring 6(FIG. 1) over the two legs 2 of the wire preform 1 and positioning it atthe region where the glass bead 5 is to be formed thereon, and thensuitabl heating the glass ring 6, as by means-of gas fires 7 directedthereagainst, for example, to cause the glass of which the ring 6 ismade to soften and fiow around the two legs 2 of the wire preform 1 soas to coalesce into a bead 5 em bedding the wire legs 2 and rigidlytying them together. As shown in FIG. 2, the glass bead 5 is formed to asize such that its maximum lateral or width dimension B is less than thespan A of the bight portion 3 of the wire preform 1, with the lateralboundaries of the glass bead 5 lying wholly within the lateralboundaries of the bight portion 3 defined by the opposite ends thereof.

A filament 8 of tungsten or other refractory metal wire is next securedat its opposite ends to the bight portion 3 of the wire preform 1 atspaced points therealong. The filament 8 may either be of coiled orcoiled-coiled form or of uncoiled form, and it is secured to the bightportion 3 of the wire preform 1 by pressing the uncoiled end legs of thefilament into the 'body of the bight portion 3 of the wire preform 1 bymeans of suitable pressing jaws. In the particular case illustrated, thefilament 8 is in the form of a singly-coiled tungsten wire of U-shapedconfiguration having a maximum lateral width dimension C (FIG. 3) lessthan the span A of the bight portion 3 of the wire preform 1 and mountedapproximately centrally on the bight portion 3 so that the lateralboundaries of the filament are located wholly within the lateralboundaries of the bight portion 3 defined by the opposite ends thereof.The appreciable transverse extent of the bight portion 3 permits acertain amount of latitude in the lateral positioning of the filament 8relative to the wire preform 1 for its attachment thereto. As a result,the positioning of the filament for mounting on the leading-in wires ofthe mount is not a critical operation to perform such as it is in thecase of the previous type mount constructions where the filament endlegs must be precisely located in side-by-side parallel alignment withthe straight inner leads of the mount for their attachment thereto. Theelimination of this critical filament positioning requirement thereforerenders feasible the fabrication, by conventional type automatic mountmaking machines, of lamp mounts according to the invention even in theextremely small sizes described hereinabove.

Simultaneously with or following the attachment of the filament 8 to thebight portion 3 of the wire preform 1, the bight portion 3 is suitablysevered at its mid-region, between its points of connection to thefilament 8, to thereby divide the wire preform into two separateleadingin wires 9 having their severed bight ends 10 spaced apart so asto be out of contact with one another. The severing of the bight portion3 of the wire preform 1 completes the fabrication of the lamp mount 11(FIG. 4). According to the preferred form of the invention, the facingor opposing severed ends of the inwardly bent ends 10 of the leading-inwires 9, formed by the severing of the bight portion 3 of the wirepreform 1, are displaced relative to one another, in a direction normalto the plane of the lead-in wires 9, so as to be offset and thus out ofcontact with one another, as shown in FIG. 5. This offsetting of thebent inner ends 10 of the lead-in wires 9 may be performedsimultaneously with the severing of the bight portion 3 of the wirepreform 1. Instead of severing the bight portion 3 of the wire preform 1and offsetting the resulting bent inner end portions 10 of theleading-in wires 9 so as to be out of contact with one another, a shortmid-section may be cut out of the bight portion 3, as shown at 12 inFIG. 6, to form the modified lamp mount construction 13.

In the formation of a finished lamp incorporating a lamp mount 11 or 13according to the invention, the lamp mount is first sealed into one endof a glass tube 14, as shown in FIG. 7. To this end, the lamp mount 11or 13 is inserted into the glass tube 14 and positioned in propersealing relation thereto with its glass bead 5 located within an end ofthe glass tube and with the bent inner ends 10 of the lead-in wires 9extending transversely across the interior of the glass tube. The glasstube 14 is of an inside diameter such that the tube will have a closetolerance sliding fit over the bends 15 in the leading-in Wires 9 at thebent inner ends 10 thereof. This close sliding fit between the glasstube 14 and the bends 15 in the leadingin wires 9 thus serves toposition the filament 8 of the lamp mount 11 more or less centrallywithin the glass tube during the sealing of the mount into the glasstube 14. As shown in FIG. 7, the sealing of the mount 11 into the glassbulb 14 may be effected by suitably heating the end of the glass tubesurrounding the bead 5 of the mount 11, as by means of gas fires 16directed against the end of the glass tube, to fuse and soften the glassof the tube as well as the glass of the head 5 to cause them to coalesceand fuse together to thereby form a sealed tube end 17 (FIG. 8).

After the sealing of the mount 11 into one end of the glass tube 14, theglass tube is then necked-in at an intermediate region thereof a shortdistance inwardly of the tube from the filament 8 therein, by suitablyheating and softening the said region of the glass tube, as by means ofgas fires 18 directed thereagainst, and then stretching the softenedintermediate section of the glass tube by axially displacing theopposite ends of the glass tube away from one another so as to attenuatethe softened glass intermediate region and form the necked-in section19. The glass tube 14 is then evacuated through its open end and itsnecked-in section 19 then tipped off in the manner customary in the lampmaking art, by directing gas tipping-off fires 20 against theintermediate neckedin section 19 of the glass tube at the region nearestthe mount-containing end thereof, to cause the glass of the necked-insection 19 to soften and coalesce so as to form an exhaust tip 21 (FIG.10) hermetically sealing off the portion 22 of the glass tube withinwhich the filament 8 is located, the portion 22 of the glass tube thusbecoming the envelope of the finished lamp. To improve the appearance ofthe finished lamp and also improve the light transmittance thereofthrough its tipped-off end, the exhaust tip 21 on the lamp envelope 22may be suitably removed as by a grinding operation to thereby form asmooth rounded top end 23, as shown in FIG. 11.

Where desired, the lamp made according to the invention may be providedwith a conventional type lamp base 24, as shown in FIG. 12. The base 24is suitably secured to the glass envelope 22 of the lamp, as by means ofa conventional type basing cement, for instance, and it may comprise aside shell contact 25 and an end contact 26 to which the leading-inwires 9 of the lamp are respectively connected.

Although preferred embodiments of my invention have been disclosed, itWill be understood that the invention is not to be limited to thespecific procedures described, but that they may be widely modifiedwithin the spirit and scope of my invention as defined by the appendedclaims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. The method of making an electric incandescent lamp mount structurewhich comprises the steps of forming a hairpin-shaped leading-in wirepreform having side-byside leg portions, fusion-sealing a glass beadaround the two legs of the said wire preform to rigidly tie themtogether, attaching the opposite ends of a filament of refractory metalto the bight portion of said wire preform at spaced points therealong,and then severing the said bight portion of the wire preform at a regionbetween the said points of attachment thereof to said filament tothereby divide the wire preform into two separate leading-in wires withtheir adjacent severed bight ends spaced apart so as to be out ofcontact with one another.

2. The method of making an electric incandescent lamp mount structure asspecified in claim 1 wherein the said hairpin-shaped wire preform isformed with its bight end of appreciably wider span than the adjacentportions of its two legs between the bight and the said glass bead.

3. The method of making an electric incandescent lamp mount structure asspecified in claim 1 wherein the said attachment of the filament to thesaid wire preform and the severing of the said bight portion thereof areperformed simultaneously.

4. The method of making an electric incandescent lamp mount structure asspecified in claim 1 wherein the said severing of the bight portion ofsaid wire preform is effected by cutting out a short section of thebight portion at the center region thereof.

5. The method of making an electric incandescent lamp mount structure asspecified in claim 1 and comprising the further step of laterallydisplacing the severed ends of the bight portion of said wire preform soas to be offset from one another.

6. The method of making an electric incandescent lamp mount structure asspecified in claim 5 wherein the steps of attaching the filament to thebight portion of said wire preform, and the severing of the bightportion and offsetting of the severed bight ends relative to one an-.

other, are all performed simultaneously.

7. The method of making an electric incandescent lamp having a tubularglass envelope which comprises the steps of forming a hairpin-shapedleading-in wire preform with its bight portion having an appreciablygreater span than the adjacent portions of its two legs such as to havea close tolerance sliding fit crosswise within the said tubularenvelope, fusion-sealing a glass bead around the two legs of said wirepreform at a region thereof closely adjacent its said bight portion,attaching the opposite ends of a configurated filament of refractorymetal to the bight portion of said wire preform at spaced pointstherealong with the lateral boundaries of the filament lying whollywithin the lateral boundaries of the opposite ends of said bight portiondefined by the bends in said wire preform, severing the said bightportion of the wire preform at a region between the points of attachmentthereof to said filament to thereby divide the wire preform into twoseparate leading-in wires and form a lamp mount, inserting the said lampmount into a glass tube with the said bends in the leading-in wires ofthe mount in close sliding fit relation to the inner wall of the glasstube to thereby position the said mount centrally within the glass tube,heating and fusing an end of said glass tube to the glass bead of saidmount, evacuating said glass tube through its open other end, and thenheating and fusing the said other end of the glass tube to hermeticallyseal it off.

8. The method of making an electric incandescent lamp as specified inclaim 7 wherein the said glass bead fusionsealed around the leading-inwires is formed with its lateral boundaries lying wholly within thelateral boundaries of the opposite ends of the bight portion of saidwire member defined by the bends therein.

References Cited UNITED STATES PATENTS 2,315,504 4/1943 Curtis 2925.15X2,486,065 10/1949 Saucet 29-25.11X 2,508,979 5/1950 Van gessel 2925.16X2,644,100 12/1955 Braundsdorff 2925.15X 3,391,298 7/1968 Dorota29-25.16X 3,396,298 8/1968 Kuryla 2925.11X 3,465,401 9/1969 Lowery, Jr.et al. 2925.15X

JOHN F. CAMPBELL, Primary Examiner R. B. LAZARUS, Assistant Examiner US.Cl. X.R. 2925.13

